In the COVID-19 group, S1 and S2 SARS-CoV-2 SIgA/IgA positively correlated with HCoV-OC43 SIgA/IgA and SIgM/IgM, HCoV-229E SIgA/IgA, and SIgM/IgM, but did not correlate with HCoVs IgG (Figure 5). The gene discussed is CD79A; the disease is COVID-19.